Light sensor having transparent substrate and diffuser formed therein

ABSTRACT

A light sensor is described that includes a glass substrate having a diffuser formed therein and at least one color filter integrated on-chip (i.e., integrated on the die of the light sensor). In one or more implementations, the light sensor comprises a semiconductor device (e.g., a die) that includes a semiconductor substrate. At least one photodetector (e.g., photodiode, phototransistor, etc.) is formed in the substrate proximate to the surface of the substrate. The color filter is configured to filter light received by the light sensor to pass light in a limited spectrum of wavelengths (e.g., light having wavelengths between a first wavelength and a second wavelength) to the photodetector. A glass substrate is positioned over the substrate and includes a diffuser. The diffuser is configured to diffuse light incident on the diffuser and to pass the diffused light to the at least one color filter for further filtering.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Application Ser. No. 61/436,507, entitled LIGHT SENSORHAVING IR CUT INTERFERENCE FILTER FORMED ON A GLASS SUBSTRATE, filed onJan. 26, 2011; U.S. Provisional Application Ser. No. 61/490,568,entitled LIGHT SENSOR HAVING GLASS SUBSTRATE WITH LENS FORMED THEREIN,filed on May 26, 2011; and U.S. Provisional Application Ser. No.61/491,805, entitled LIGHT SENSOR HAVING GLASS SUBSTRATE WITH LENSFORMED THEREIN, filed on May 31, 2011. U.S. Provisional Application Ser.Nos. 61/436,507; 61/490,568; and 61/491,805 are herein incorporated byreference in their entireties.

BACKGROUND

Electronic devices, such as smart phones, tablet computers, digitalmedia players, and so forth, increasingly employ light sensors tocontrol the manipulation of a variety of functions provided by thedevice. For example, light sensors are commonly used by electronicdevices to detect ambient lighting conditions in order to control thebrightness of the device's display screen. Typical light sensors employphotodetectors such as photodiodes, phototransistors, or the like, whichconvert received light into an electrical signal (e.g., a current orvoltage).

Light sensors are commonly used in gesture sensing devices. Gesturesensing devices enable the detection of physical movement (e.g.,“gestures”) without the user actually touching the device within whichthe gesture sensing device resides. The detected movements can besubsequently used as input commands for the device. In implementations,the electronic device is programmed to recognize distinct non-contacthand motions, such as left-to-right, right-to-left, up-to-down,down-to-up, in-to-out, out-to-in, and so forth. Gesture sensing deviceshave found popular use in handheld electronic devices, such as tabletcomputing devices and smart phones, as well as other portable electronicdevices, such as laptop computers, video game consoles, and so forth.

SUMMARY

A light sensor is described that includes an IR suppression filter(e.g., any type IR interference based filter) and at least onephotodetector integrated on-chip (i.e., integrated on the die of thelight sensor) with a transparent substrate. In one or moreimplementations, the light sensor comprises a semiconductor device(e.g., a die) that includes a semiconductor substrate. Photodetectors(e.g., photodiodes, phototransistors, etc.) are formed in the substrateproximate to the surface of the substrate. A IR suppression filter ispositioned over the photodetectors. The IR suppression filter isconfigured to filter infrared light from light incident on the lightsensor to at least substantially block infrared light from reaching thephotodetectors. A buffer layer is formed over the surface of thesubstrate. In an implementation, a transparent substrate is coupled tothe IR suppression filter to provide support to the IR suppressionfilter. In another implementation, the transparent substrate may beattached to the wafer (e.g., substrate wafer) with another buffer (e.g.,adhesion) layer. In yet another implementation, the IR suppressionfilter may be positioned over the surface of the substrate so that thebuffer layer is between the glass wafer and the substrate wafer. Thephotodetectors may also comprise one or more clear photodetectorsconfigured to detect the ambient light environment.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

DRAWINGS

The detailed description is described with reference to the accompanyingfigures. The use of the same reference numbers in different instances inthe description and the figures may indicate similar or identical items.

FIG. 1A is a diagrammatic partial cross-sectional side view illustratinga light sensor having an IR suppression filter formed on a transparentsubstrate, a plurality of color pass filters, and a buffer layer inaccordance with an example implementation of the present disclosure.

FIG. 1B is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 1A, whereinthe IR suppression filter is disposed above the plurality of color passfilters.

FIG. 1C is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 1A, whereinthe light sensor further includes a through-substrate via.

FIG. 1D is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 1B, whereinthe light sensor further includes a dark edge disposed over the IRsuppression filter.

FIG. 2A is a diagrammatic partial cross-sectional side view illustratingan implementation of the light sensor depicted in FIG. 1A, where thelight sensor also includes a dark current sensor.

FIG. 2B is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 2A, whereinthe IR suppression filter is disposed above the plurality of color passfilters.

FIG. 2C is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 2A, whereinthe light sensor further includes a through-substrate via.

FIG. 2D is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 2C, whereinthe light sensor includes a plurality of color pass filters and aplurality of photodetectors.

FIG. 2E is a diagrammatic partial cross-sectional side view illustratinganother implementation of light sensor illustrated in FIG. 2D, whereinthe light sensor includes a dark edge and an IR suppression filterdisposed over the color pass filters.

FIG. 3 is a diagrammatic top plan view of multiple light sensorsdepicted in FIGS. 1 and 2, formed in a wafer.

FIG. 4 is a diagrammatic partial cross-sectional side view illustratinga light sensor comprised of a semiconductor device having aphotodetector, a plurality of color filters, and a transparent substratehaving a lens in accordance with an example implementation of thepresent disclosure.

FIG. 5 is a diagrammatic partial cross-sectional view illustrating alight sensor in accordance with another example implementation of thepresent disclosure, where the light sensor illustrated in FIG. 4 furtherincludes a IR suppression filter.

FIG. 6 is a diagrammatic partial cross-sectional view illustrating alight sensor in accordance with another example implementation of thepresent disclosure, wherein the light sensor illustrated in FIG. 4 isconfigured for backside illumination.

FIG. 7 is a flow diagram illustrating an example process in an exampleimplementation for fabricating light sensors with an IR suppressionfilter and a transparent substrate, such as the sensor shown in FIG. 1A.

FIGS. 8 through 10 are diagrammatic partial cross-sectional sideillustrating example fabrication steps of the light sensor illustratedin FIG. 1 in accordance with the techniques illustrated in FIG. 4,wherein FIG. 5 illustrates the photodetectors and a bond pad formed inthe substrate; FIG. 6 illustrates color pass filters formed over thephoto detectors; and FIG. 7 illustrates a buffer layer formed over thecolor pass filters and the IR suppression filter formed on a transparentsubstrate.

FIG. 11 is a flow diagram illustrating an example process in an exampleimplementation for fabricating light sensors with an IR suppressionfilter and a transparent substrate, wherein the light sensors includethe IR suppression filter positioned over a buffer layer thatencapsulates the plurality of color pass filters.

FIG. 12 is a flow diagram illustrating a process in an exampleimplementation for fabricating light sensors, such as the sensor shownin FIG. 4.

FIGS. 13 through 27 are diagrammatic partial cross-sectional sideelevation views illustrating the fabrication of a light sensor, such asthe sensor shown in FIG. 4, in accordance with the process shown in FIG.12.

DETAILED DESCRIPTION

Overview

To filter infrared light, light sensors may employ infrared blockingfilters to reduce the transmission of infrared light, while passingvisible light to the photodetector array of the light sensor. Such IRblocking filters are comprised of IR suppressing material appliedexternally to the light sensor package following fabrication of thepackage or included in the component during packaging. Thisconfiguration effectively blocks infrared light from reaching thephotodiodes, but also substantially reduces the amount of infrared lightthat reaches the infrared photodetectors of the light sensor.Consequently, the sensitivity of the resulting light sensor to infraredlight is reduced. Additionally, visible light sensors may employsubtraction techniques (i.e., subtraction circuits) to remove infraredlight at the wafer level. However, spacing constraints restrict die areaavailable for color pass filters, photodetectors, and subtractioncircuits to continue to be utilized on the same chip as more photodetectors are required to detect light in a limited spectrum ofwavelengths (e.g., “blue” light, “green” light, “red” light, etc.).

Accordingly, a light sensor is described that includes an IR suppressionfilter and at least one color pass filter integrated on-chip (i.e.,integrated on the die of the light sensor). In one or moreimplementations, the IR suppression filter may be an IR cut filter, anotch interference filter, an absorption based filter, or a diffractionbased filter. In one or more implementations, the light sensor isfabricated as a semiconductor device that comprises a die having asubstrate. Photodetectors such as photodiodes, phototransistors, or thelike, are formed in the substrate proximate to the surface of thesubstrate. One or more color pass filters are provided over thephotodetectors. The color pass filters are configured to filter visiblelight received by the light sensor to pass light in a limited spectrumof wavelengths (e.g., light having wavelengths between a firstwavelength and a second wavelength) to at least one of thephotodetectors. For example, color pass filters (e.g., red, green, bluefilters) may be formed on the surface of the substrate and aligned overthe one or more photodetectors.

An IR suppression filter is positioned over the color pass filters. TheIR suppression filter is configured to filter infrared light from lightreceived by the light sensor to at least substantially block infraredlight from reaching the photodetectors. However, the IR suppressionfilter may be selectively positioned so that it does not block infraredlight to infrared photodetectors of the light sensor. Duringfabrication, a buffer layer is formed on the surface of the substrate atwafer level to at least substantially encapsulate and enclose the colorpass filters to protect the filters during further processing steps andto planarize the wafer. The IR suppression filter is formed on atransparent substrate, and positioned proximate to the surface of thebuffer layer over the photodetectors. The transparent substrate isconfigured to facilitate formation of the IR suppression filter, and toprovide support to the IR suppression filter during fabrication of thelight sensor. In another implementation, the IR suppression filter maybe formed over the color pass filters, which are formed over the bufferlayer. In this implementation, an adhesion layer is formed over thebuffer layer and functions to bond the transparent substrate to thewafer substrate.

The photodetectors may also comprise one or more clear photodetectorsconfigured to receive light that is not filtered by a color pass filter,thereby allowing the clear photodetector to detect the ambient lightenvironment.

In the following discussion, example implementations of light sensorsare first described. Example procedures are then discussed that may beemployed to fabricate the example light sensor.

Example Implementations

FIGS. 1A through 3 illustrate light sensors 100 in accordance with anexample implementation of the present disclosure. As shown, the lightsensors 100 comprise semiconductor devices that include a die having asubstrate 102. The substrate 102 furnishes a base material utilized toform one or more electronic devices through various fabricationtechniques such as photolithography, ion implantation, deposition,etching, and so forth. The substrate 102 may comprise n-type silicon(e.g., a silicon doped with a group carrier element, such as a group Velement (e.g., phosphorus, arsenic, antimony, etc.), to furnish n-typecharge carrier elements to the silicon) or p-type silicon (e.g., silicondoped with a group carrier element, such as a group IIIA element (e.g.,boron, etc.), to furnish p-type charge carrier elements to the silicon,or other group elements to furnish p-type charge carrier elements). Thesubstrate 102 may further be comprised of one or more insulating layers104 and may include a silicon dioxide layer 104A and a silicon nitridelayer 104B. While a silicon substrate is described, it is understoodthat other types of substrates may be utilized without departing fromthe scope of this disclosure. For example, the substrate 102 may becomprised of silicon-germanium, gallium-arsenide, or the like.

The substrate 102 is illustrated as having a surface 106. An array ofphotodetectors (photodetectors 108, 120, 122 are shown) is formed in thesubstrate 102 proximate to the surface 106. The photodetectors 108, 120,122 within the array may be configured in a variety of ways. Forexample, the photodetectors 108, 120, 122 may be comprised of a photosensor diode, a phototransistor, or the like. In an implementation, thephotodetectors 108, 120, 122 are capable of detecting light andproviding a signal in response thereto. The photodetectors 108, 120, 122may provide a signal by converting light into current or voltage basedupon the intensity of the detected light. Thus, once a photodetector108, 120, 122 is exposed to light, multiple free electrons may begenerated to create a current. The photodetectors 108, 120, 122 areconfigured to detect light in both the visible light spectrum and theinfrared light spectrum. As used herein, the term light is contemplatedto encompass electromagnetic radiation occurring in the visible lightspectrum and the infrared light spectrum. The visible light spectrum(visible light) includes electromagnetic radiation occurring in therange of wavelengths from approximately three hundred and ninety (390)nanometers to approximately seven hundred and fifty (750) nanometers.Similarly, the infrared light spectrum (infrared light) includeselectromagnetic radiation that ranges in wavelength from approximatelyseven hundred (700) nanometers to approximately three hundred thousand(300,000) nanometers. In an implementation, complementarymetal-oxide-semiconductor (CMOS) fabrication techniques may be utilizedto form the photodetectors 108, 120, 122. In another implementation,bipolar fabrication techniques may be utilized to form thephotodetectors 108, 120, 122. In yet another implementation, BiCMOSfabrication techniques may be utilized to form the photodetectors 108,120, 122.

Color pass filters 110 are illustrated proximate to the surface 106. Thecolor pass filters 110 are configured to filter visible light receivedby the light sensor 100 to pass light in a limited spectrum ofwavelengths (e.g., light having wavelengths between a first wavelengthand a second wavelength) to at least one of the photodetectors 108. Inan implementation, the color pass filters 110 may comprise absorptionfilters that allow visible light in a limited spectrum of wavelengths topass through the filter, while blocking (e.g., absorbing or reflecting)visible light within a second spectrum of wavelengths. Thus, the colorpass filter 110 may be substantially transparent for visible lightwithin a first spectrum of wavelengths, and substantially opaque withina second spectrum of wavelengths. In another implementation, the colorpass filter 110 may comprise an interference filter that allows visiblelight to pass in a specified range of wavelengths.

A plurality of color pass filters 110 may be provided. For example, thelight sensor 100 may comprise a first color pass filter 110A configuredto filter visible light and to pass light having a first limitedspectrum of wavelengths (e.g., wavelengths between a first wavelengthand a second wavelength), a second color pass filter 110B configured tofilter visible light and pass light having a second limited spectrum ofwavelengths (e.g., wavelengths between a third wavelength and a fourthwavelength), and a third color pass filter 110C configured to filtervisible light and pass light having a third spectrum of wavelengths(e.g., wavelengths between a fifth wavelength and a sixth wavelength),and so forth. In the example illustrated, the light sensor 100 iscomprised of an array of three different color pass filters 110: a first(blue) color pass filter 110A configured to transmit a “blue” visiblelight (i.e., visible light with a wavelength between approximately fourhundred fifty (450) nanometers and approximately four hundredseventy-five (475) nanometers); a second (green) color pass filter 110Bconfigured to transmit a “green” visible light (i.e., visible light witha wavelength between approximately four hundred ninety-five (495)nanometers and approximately five hundred and seventy (570) nanometers);and a third (red) color pass filter 110C configured to transmit a “red”visible light (i.e., visible light with a wavelength betweenapproximately six hundred and twenty (620) nanometers and approximatelyseven hundred and fifty (750) nanometers). It is contemplated that othervisible light color pass filters 110 may be employed. The color passfilters 110 are combined with the IR suppression filter 116 since thecolor pass filters 110 may pass infrared light as well. For instance,color pass filters 110 configured to transmit visible light havinglimited spectrums of wavelengths typically associated with the colors ofcyan, magenta, yellow, and so forth may be utilized. The color passfilters 110 are selectively arrayed over the photodetectors 108 to allowvisible light in a desired limited spectrum of wavelengths to passthrough the color pass filter 110 to the photodetector 108. For example,as shown in FIGS. 1A through 2B, the first color pass filter 110A ispositioned over a first photodetector 108A, the second color pass filter110B is positioned over a second photodetector 108B, and the thirdfilter 110C is positioned over a third photo detector 108C.

In the implementations illustrated in FIGS. 1A through 2B, the colorpass filters 110 are formed over the surface 106 using suitabledeposition techniques such as spin coating and/or photo patterning (forabsorption filter 110 formation). Likewise, suitable sputtering andplating techniques may be utilized for color interference filter 110formation. In an example implementation, the color pass filters 110 havea thickness of approximately one (1) micron. However, it is contemplatedthat color pass filters 110 having lesser or greater thicknesses arepossible. The color pass filters 110 may be formed on an adhesion layer112 to hold the color pass filters 110 in position upon completion ofthe deposition techniques.

In one or more implementations, the color pass filters 110 may employone or more color pass filters to further filter light (e.g., infraredlight, etc.). In an implementation, a single color pass filter 110(e.g., color pass filter 110A) may include a first color pass filterconfigured to filter visible light and to pass light having a firstlimited spectrum of wavelengths and a second color pass filterpositioned over the first color pass filter that is configured to filtervisible light and to pass light having a second limited spectrum ofwavelengths. For example, a single color pass filter 110 may include a“blue” color pass filter positioned over a “red” color pass filter tofurther filter light. However, it is contemplated that other colors maybe utilized (e.g., red over green color pass filter configuration, blueover green color pass filter configuration, etc.).

A buffer layer 114 is formed over the surface 106 of the substrate 102to encapsulate and provide protection to the color pass filters 110. Inthe implementation shown in FIGS. 1A through 2B, the color pass filters110 are formed on the surface 106 of the substrate 102. For instance,the color pass filters 110 are formed on the adhesion layer 112, whichis formed on the surface 106. The buffer layer 114 is then applied tothe surface 106 of the substrate 102 over the color pass filters 110. Inthis implementation, the buffer layer 114 at least substantiallyencapsulates, or encloses, the color pass filters 110 to protect thefilters during further processing steps. The buffer layer 114 may becomprised of a polymer material such as Benzocyclobutene (BCB) polymer,or the like. However, it is contemplated that other buffer material maybe used.

An IR suppression filter 116 is illustrated as positioned over thephotodetectors 108 on the top surface 106 of the substrate 102. The IRsuppression filter 116 is configured to filter infrared light from lightreceived by the light sensor to at least substantially block infraredlight from reaching the photodetectors 108, 122. For instance, in one ormore specific implementations, an IR suppression filter 116 may beprovided that is capable of blocking approximately fifty (50) to onehundred (100) percent of infrared light (i.e., light in the infraredspectrum) incident on the photodetectors 108, 122 while at leastsubstantially passing (e.g., passing approximately greater than fifty(50) percent) visible light (i.e., light in the visible spectrum) to thephotodetectors 108, 122. However, the aforementioned values (e.g.,percentage values representing the proportion of infrared light blockedand/or passed by the IR suppression filter 116) may depend on particularapplication requirements of the light sensor 100. Thus, IR suppressionfilters 116 that are capable of blocking a higher or lower proportion ofinfrared light and/or of transmitting a higher or lower proportion ofvisible light are contemplated.

The IR suppression filter 116 may be configured in a variety of ways.For example, the IR suppression filter 116 may be comprised of a numberof layers and/or a number of materials to at least partially suppressinfrared light. It is contemplated that a various number of layersand/or materials may be utilized depending upon the amount of IRsuppression desired in the light sensor 100. For example, in animplementation, the IR suppression filter 116 may comprise a multi-layerstructure that includes at least two (2) different materials thatcomprise different refractive indices. The IR suppression filter 116 maybe approximately one (1) to approximately fifteen (15) microns thickand/or approximately ten (10) to approximately one hundred and twenty(120) layers thick. In a specific implementation, the IR suppressionfilter 116 may be approximately ten (10) microns thick. However, it iscontemplated that the IR suppression filter 116 may have otherconstructions and/or thicknesses.

In an implementation, a transparent substrate 118 is provided over theIR suppression filter 116 as illustrated in FIGS. 1A through 2B tofacilitate formation of the IR suppression filter 116 and to furnishsupport to the IR suppression filter 116 during fabrication of the lightsensor 100. In another implementation, the IR suppression filter 116 maybe attached to the transparent substrate 118 and positioned over thelight sensor 100. While the transparent substrate 118 (and the IRsuppression filter 116 in FIG. 1A) is illustrated as being flush (e.g.,even) with the adhesion layer 112 (see FIG. 1A) and with the bufferlayer 114A (see FIG. 1B), it is contemplated that the transparentsubstrate 118 (and the IR suppression filter 116) may not necessarily beflush with (e.g., the transparent substrate 118 extends past) theadhesion layer 112 or the buffer layer 114A (e.g., due to processingvariations, etc.). The transparent substrate 118 is configured to betransparent to light occurring within wavelengths of interest. Forexample, the transparent substrate 118 may be at least substantiallytransparent to light occurring within a limited spectrum of wavelengths(e.g., transparent to light occurring within the infrared wavelengthspectrum and not transparent to light occurring within the visiblewavelength spectrum, or vice versa). The transparent substrate 118 maybe configured in a variety of ways. For example, the transparentsubstrate 118 may be a glass substrate. Thus, the glass substrate mayhave an anti-reflection coating that is at least substantiallytransparent (i.e., a low refractive index) to allow the light incidenton the glass substrate to substantially pass through (i.e., lowreflective metric) to the IR suppression filter 116. The IR suppressionfilter 116 may be formed on the transparent substrate 118 at wafer levelusing a suitable deposition technique. In such implementations, thetransparent substrate 118 may be used to pattern the IR suppressionfilter 116. For example, the transparent substrate 118 may include oneor more apertures formed therein. When the IR suppression filter 116 isformed on the transparent substrate 118, the IR suppression filter 116may include one or more apertures aligned with the apertures oftransparent substrate 118. In another implementation, which is shown inFIGS. 1B and 2B, the color pass filters 110 are formed over the surface106 and then a first buffer layer 114A is then formed over the colorfilters 110. The IR suppression filter 116 is then formed over the firstbuffer layer 114A. A second buffer layer 114B (e.g., an insulatinglayer) is then formed over the substrate 102.

In one or more implementations, the light sensor 100 may be configuredto include one or more infrared photodetectors 120 (i.e., photodetectors108 that are configured to detect light in the infrared spectrum formedin the substrate 102 of the light sensor 100 die). These photodetectors120 detect infrared light (i.e., light in the infrared spectrum) thatmay, for example, be transmitted by an infrared transmitter (e.g., aninfrared light emitting diode (LED)) as part of a proximity sensorimplemented in the electronic device. Accordingly, the IR suppressionfilter 116 may be patterned so that it does not block the reception ofinfrared light (i.e., light in the infrared spectrum) by the infraredphotodetectors 120, thereby increasing the sensitivity of the lightsensor to infrared light and improving the performance of devices thatemploy the light sensor 100 (e.g., the proximity sensor in an electronicdevice).

The array of photodetectors 108 may further include one or more clearphotodetectors 122 configured to receive light that is not filtered by acolor pass filter 110. As illustrated, the clear photodetectors 122 maybe positioned in the substrate 102 so that they are positioned under theIR suppression filter 116 but are not located below a color pass filter110. Thus, the clear photodetectors 122 detect light within a spectrumof wavelengths corresponding to several visible colors (i.e., light fromthe visible spectrum). In this manner, the clear photodetectors 122 maybe used to detect visible ambient lighting conditions absent infraredinterference.

The clear photodetectors 122 may be configured in a variety of ways. Forexample, like the other photodetectors 108 within the array, the clearphotodetector(s) 122 may comprise a photodiode, a phototransistor, orthe like, that is capable of detecting light by converting light intocurrent or voltage. In an implementation, the signal (e.g., current orvoltage) produced by the clear photodetectors 122 is based upon (e.g.,proportional to) the detected intensity of visible light received. Thus,the clear photodetectors 122 may be used to detect the intensity of theambient light level outside of a portable electronic device in which thelight sensor 100 is integrated. The resulting measure of ambient lightintensity may be utilized by various applications running in theportable electronic device. For example, an application of the portableelectronic device may control the brightness of a display screen basedupon the ambient light intensity.

As shown in FIGS. 2A and 2B, the light sensor 100 may also include adark current sensor 124, which may be formed in the substrate 102 andproximate to the insulation layer 104. The dark current sensor 124 maybe comprised of a dark photodiode, a dark phototransistor, or the like,that is configured to provide dark current (i.e., current generated by aphotodiode when the photodiode is exposed to total darkness) to lightsensor 100. The dark current sensor 124 may be configured in a varietyof ways. For example, in one implementation, the dark current sensor 124may be fabricated from a photodiode that includes a metal covering. Inanother implementation, the dark current sensor 124 may be fabricatedfrom a photodiode having a filter that is configured to at leastsubstantially block light. However, other implementations are possible.

As shown in FIGS. 1A through 2B, the light sensor 100 also includes abond pad 126 to provide connectivity to light sensor 100. In animplementation, the bond pad 126 may be comprised of an electricallyconductive area formed proximate to surface 104. For instance, the bondpad 126 may be comprised of a metal pad, a polycrystalline silicon(polysilicon) pad, or the like. The bond pad 126 may provideconnectivity functionality between various electronic circuits (notshown) residing in light sensor 100 and package pins of a package (notshown) that encloses the light sensor 100.

In another implementation, as shown in FIGS. 1C, 1D, 2C, 2D and 2E thelight sensors 100 may employ a Redistribution Layer (RDL) configuration.The RDL configuration employs a redistribution structure 132 comprisedof a thin-film metal (e.g., aluminum, copper, etc.) rerouting andinterconnection system that redistributes conductive layers 134 to anarea array of bump interfaces 136 (e.g., UBM pads) that may be moreevenly deployed over the surface of the sensor 100. The bump interface136 is configured to provide a reliable interconnect boundary betweenthe conductive layers 134 and solder bumps 135. The bump interface 136comprises under-bump metallization (UBM) 138 applied to the conductivelayers 134 of the light sensor 100. The UBM 138 may have a variety ofcompositions. For example, the UBM 138 may include multiple layers ofdifferent metals (e.g., aluminum [Al], nickel [Ni], copper [Cu], etc.)that function as an adhesion layer, a diffusion barrier layer, asolderable layer, an oxidation barrier layer, and so forth. However,other UBM structures are possible.

In an implementation, as shown in FIGS. 1C, 2C, 2D, and 2E, the IRsuppression filter 116 and the transparent substrate 118 may extend overthe sensor 100. For instance, in a specific example, the IR suppressionfilter 116 and the transparent substrate 118 extend over the entirebuffer layer 114.

As described above, the transparent substrate 118 and the IR suppressionfilter 116 include apertures such that the transparent substrate 118does not extend over the infrared photodetectors 120, the dark currentsensor 124, or the bond pad 126 when the IR suppression filter 116 andthe transparent substrate 118 are positioned over the buffer layer 114as shown in FIGS. 1 and 2. However, in other implementations, it iscontemplated that the IR suppression filter 116 can extend over the darkcurrent sensor 124. FIG. 3 illustrates multiple light sensors 100fabricated on a wafer 144 and the transparent substrate 118 positionedover the wafer 144. The transparent substrate 118 includes multipleapertures (represented as the space enclosed by rectangle 128)positioned over infrared photodetectors 120 and bond pad 126. Thus, theIR suppression filter 116 also includes apertures aligned with thetransparent substrate 118's apertures such that the IR suppressionfilter 116 does not cover (i.e., allows visible light and infrared lightto pass unfiltered) infrared photodetectors 120 or the bond pad 126.

An insulating material 130 may be applied over the surface 106 of thesubstrate 102 to provide encapsulation and protection to the variousstructures of sensor 100 (e.g., the photodetectors 108, the color passfilters 110, the buffer material 114, the IR suppression filter 116, andso forth). In one or more implementations, the insulating material 130is an epoxy material. However, other insulating materials may be usedand are contemplated. The insulating material 130 may be selectivelyremoved (e.g., etched) to provide access to the bond pad 126, and so on.Furthermore, as shown in FIGS. 1C and 2C, an insulating material 130 maybe applied proximate to the redistribution structure 132 to providefurther insulation and encapsulation to the photodetectors 108, 122.However, with the implementation shown in FIGS. 1C, 2C, 2D, and 2E, itis contemplated that an opening may be provided to the pad 126 from thefront side.

The sensor 100 may also include a dark edge 140 configured to at leastsubstantially eliminate impingement of light that does not pass throughthe IR suppression filter 116 to the photodetectors 108, 122 (see FIGS.1D and 2E). The dark edge 140 is formed of an opaque material that doesnot transmit light (visible light and infrared light). The dark edge 140may be configured in a variety of ways. For instance, in a specificexample, the dark edge 140 may be positioned over select portions (e.g.,not directly over the color pass filters 110) of the buffer layer 114.In another example, the dark edge may be positioned over select portions(e.g., not directly over the color pass filters 110) of the transparentsubstrate 118, positioned over the side of the buffer layer 116 and thetransparent substrate 118, combinations thereof, or the like. However,it is contemplated that the dark edge 140 may have a variety of patternsdepending on application requirements.

In various implementations, the light sensors 100 described herein maybe configured to detect a surrounding light environment and/or toprovide infrared light detection (e.g., for use as a proximity sensor).The color pass filters 110 are configured to filter visible light andpass light in a limited spectrum of wavelengths to the respectivephotodetectors 108. The photodetectors 108 generate a signal (e.g.,current value) based upon the intensity of the light. The IR suppressionfilter 116 is configured to filter infrared light to substantially blockinfrared light from reaching the photodetectors 108, 122. The clearphotodetector(s) 122 detect ambient lighting conditions absent colorfiltration and generate a signal (e.g., a current value) based upon theintensity of visible light detected. The signal generated by thephotodetectors 108 and the clear photodetector(s) 122 may be utilized byother circuit devices and/or applications to control various aspects ofa portable electronic device (e.g., control the brightness of thedevice's display screen, to turn off backlighting to conserving batterylife, and so forth). Infrared photodetectors 120 detect infrared light(e.g., light in the infrared spectrum) and generate a signal (e.g., acurrent value) based upon the intensity of the infrared light detected.The signal generated by the infrared photodetectors 120 may be utilizedby other circuit devices and/or applications to control various aspectsof a portable electronic device. For example, infrared light may betransmitted by an infrared transmitter (e.g., an infrared light emittingdiode (LED)) and detected by the infrared photodetectors 120 of thelight sensor 100 as part of an infrared image sensor or a proximitysensor implemented in an electronic device. The IR suppression filter116 may be positioned so that it does not block the reception ofinfrared light by the infrared photodetectors 120, thereby increasingthe sensitivity of the light sensor 100 to infrared light and improvingthe performance of devices that employ the light sensor 100.

FIGS. 4 through 6 illustrate light sensors in accordance with furtherexample implementations of the present disclosure. As shown, the lightsensors 200 further include color filters 202 (e.g., such as the colorpass filters 110 described above). The color filters 202 are configuredto pass light in a limited spectrum of wavelengths (e.g., light havingwavelengths between a first wavelength and a second wavelength) to thephotodetector 108. For example, the color filters 202 may be configuredto pass light generated by the illumination source and to block lighthaving wavelengths that are different than the illumination source(e.g., light occurring in a second wavelength). It is contemplated thatthe color filters 202 may comprise absorption filters. In oneimplementation, the color filters 202 allow light in a limited spectrumof wavelengths to pass through the filter, while blocking (e.g.,reflecting or absorbing) light within a second spectrum of wavelengths.Thus, the color filters 202 may be substantially transparent for lightwithin a first spectrum of wavelengths, and substantially opaque forlight within a second spectrum of wavelengths. In implementations, thecolor filters 202 may comprise multilayer structures having variedthicknesses and/or numbers of layers, which may have differingthicknesses and/or refractive indices. Moreover, the color filters 202may include a diffractive grading that allows for light within the firstspectrum of wavelengths to at least substantially pass through.

As shown in FIG. 4, a plurality of color filters 202 may be employed.For example, the light sensor 200 may comprise a first colorinterference filter 202A configured to filter light and pass lighthaving a first limited spectrum of wavelengths (e.g., wavelengthsbetween a first wavelength and a second wavelength), and a second colorinterference filter 202B configured to filter light and pass lighthaving a second limited spectrum of wavelengths (e.g., wavelengthsbetween a third wavelength and a fourth wavelength), and so forth. Inthe example illustrated, the light sensor 200 is comprised of an arrayof three different color filters 202: a first (blue) color filter 202Aconfigured to transmit a “blue” visible light (i.e., visible light witha wavelength between approximately four hundred fifty (450) nanometersand approximately four hundred seventy-five (475) nanometers); and asecond (green) color filter 202B configured to transmit a “green”visible light (i.e., visible light with a wavelength betweenapproximately four hundred ninety-five (495) nanometers andapproximately five hundred and seventy (570) nanometers). It iscontemplated that other visible light color filters 202 may be employed.For instance, color filters 202 configured to transmit visible lighthaving limited spectrums of wavelengths typically associated with thecolors of cyan, magenta, yellow, and so forth, may be utilized. Thecolor filters 202 are selectively positioned over the photodetector 108to allow light in a desired limited spectrum of wavelengths to be passedto the photodetector 108. Moreover, as shown in FIG. 4, the colorfilters 202A, 202B are shown in a stacked configuration (e.g., filter202A is stacked over filter 202B) to allow for further filtering oflight. For example, a color filter 202 may employ a first color filterconfigured to filter visible light and to pass light having a firstlimited spectrum of wavelengths and a second color pass filterpositioned over the first color pass filter that is configured to filtervisible light and to pass light having a second limited spectrum ofwavelengths For example, a single color pass filter 202 may include a“blue” color pass filter positioned over a “red” color pass filter tofurther filter light. However, it is contemplated that other colors maybe utilized (e.g., red over green color pass filter configuration, blueover green color pass filter configuration, etc.). A suitable adhesive(e.g., bonding) material 112 is utilized to at least substantially holdthe color filters 202A, 202B over the photodetector(s) 108. While onlyone stacked configuration is shown, it is contemplated that otherstacked configurations may be employed. For example, the color filters202A, 202B may employ a non-stacked configuration.

As shown in FIG. 5, the light sensor 200 may further include an infrared(IR) suppression filter 116. The IR suppression filter 116 may beconfigured to pass light in a limited spectrum (e.g., a fourth spectrum)of wavelengths. For example, the IR suppression filter may be configuredto filter infrared light from light received by the light sensor 100 toat least substantially block infrared light from reaching thephotodetector 108. For instance, in an example implementation, an IRsuppression filter 116 may be provided that is capable of blockingapproximately fifty (50) to one hundred (100) percent of infrared light(i.e., light in the infrared spectrum) incident on the photodetector(s)108 while at least substantially passing (e.g., passing approximatelygreater than fifty (50) percent) visible light (i.e., light in thevisible spectrum) to the photodetector(s) 108. However, theaforementioned values (e.g., percentage values representing theproportion of infrared light blocked and/or passed by the IR suppressionfilter 116) may depend on particular application requirements of thelight sensor 200. Thus, IR suppression filters 116 that are capable ofblocking a higher or lower proportion of infrared light and/or oftransmitting a higher or lower proportion of visible light arecontemplated.

The substrate 102 may also include one or more integrated circuitdevices formed therein through various fabrication techniques such asphotolithography, ion implantation, deposition, etching, and so forth.The integrated circuits may be configured in a variety of ways. Forexample, the integrated circuits (not shown) may be digital integratedcircuits, analog integrated circuits, mixed-signal circuits, and soforth. In one or more implementations, the integrated circuits maycomprise digital logic devices, analog devices (e.g., amplifiers, etc.),combinations thereof, and so forth. As described above, the integratedcircuits may be fabricated utilizing various fabrication techniques. Forexample, the integrated circuits may be fabricated via one or moresemiconductor fabrication techniques. For example, the integratedcircuits may be fabricated via complementary metal-oxide-semiconductor(CMOS) techniques, bi-polar semiconductor techniques, and so on.

As shown in FIGS. 4 through 6, sensor 200 includes one or more areaarrays of conductive layers 134 to furnish electrical interconnectionbetween various electrical components (e.g., photodetector 108 and anintegrated circuit) associated with the sensor 200. In implementations,the conductive layers 134 may comprise one or more conductive (e.g.,contact) pads, redistribution structures, or the like. In a furtherimplementation, the conductive layers 134 may comprise seed metal and/orbarrier metal layers to allow for plated-line formation. The number andconfiguration of conductive layers 134 may vary depending on thecomplexity and configuration of the integrated circuits, and so forth.The conductive layers 134 provide electrical contacts through which theintegrated circuits are interconnected to other components, such asprinted circuit boards (not shown), when the sensors 200 are configuredas wafer-level packaging (WLP) devices or other integrated circuitsdisposed within the sensor 200. In one or more implementations, theconductive layers 134 may comprise an electrically conductive material,such as a metal material (e.g., aluminum, copper, etc.), or the like.

The conductive layer 134 may also provide electrical interconnectionwith one or more solder bumps. Solder bumps are provided to furnishmechanical and/or electrical interconnection between the conductivelayers 134 and corresponding pads (not shown) formed on the surface of aprinted circuit board (not shown). In one or more implementations, thesolder bumps may be fabricated of a lead-free solder such as aTin-Silver-Copper (Sn—Ag—Cu) alloy solder (i.e., SAC), a Tin-Silver(Sn—Ag) alloy solder, a Tin-Copper (Sn—Cu) alloy solder, and so on.However, it is contemplated that Tin-Lead (PbSn) or Nickel-Aluminum(NiAu) solders may be used.

Bump interfaces 136 may be applied to the conductive layers 134 toprovide a reliable interconnect boundary between the conductive layers134 and the solder bumps. For instance, in the sensor 200 shown in FIGS.4 and 5, the bump interface 136 comprises under-bump metallization (UBM)138 applied to the conductive layers 134 of the light sensor 100. TheUBM 138 may have a variety of compositions. For example, the UBM 138 mayinclude multiple layers of different metals (e.g., aluminum [Al], nickel[Ni], copper [Cu], etc.) that function as an adhesion layer, a diffusionbarrier layer, a solderable layer, an oxidation barrier layer, and soforth. However, other UBM structures are possible.

In one or more implementations, the sensor 200 may employ aRedistribution Layer (RDL) configuration. The RDL configuration employsa redistribution structure 132 comprised of a thin-film metal (e.g.,aluminum, copper, etc.) rerouting and interconnection system thatredistributes the conductive layers 134 to an area array of bumpinterfaces 208 (e.g., UBM pads) that may be more evenly deployed overthe surface of the sensor 200.

As shown in FIGS. 1C, 2C, 2D, 2E, 4, and 5, the sensors 100, 200 mayfurther include a through-substrate via 142 (TSV) that extends throughthe substrate 102. The TSV 142 is configured to furnish an electricalinterconnection between a first conductive landing (e.g., layer) 134A(e.g., the UBM 138) and a second conductive landing (e.g., layer) 134B(e.g., a bond pad, such as bond pad 126, proximate to the photodetector108) of the sensor 200 when the TSV 142 is filled with a conductivematerial 134. In one or more implementations, the conductive material134 may comprise a metal such as copper, or the like. The light sensor200 may employ TSVs 142 of varying dimensions depending on therequirements of the light sensor 200.

As illustrated in FIGS. 4 through 6, a transparent substrate 118 ispositioned over the first surface 104 of the substrate 102. In one ormore implementations, the transparent substrate 118 may be formed from aglass wafer, or the like, as discussed herein. The transparent substrate118 is configured to at least substantially allow for the passage oflight through the transparent substrate 118. In an implementation, thetransparent substrate 118 is configured to allow for sufficient passageof light through the transparent substrate 118. In one example, thetransparent substrate 118 is configured to at least substantially allowfor the passage of at least ninety (90) percent of light through thetransparent substrate 118. However, other percentages are contemplated.For example, the transparent substrate 118 may at least substantiallypass through light that is reflected from an object proximate (e.g.,above) to the sensor 200. The transparent substrate 118 also includes alens 204 to focus and to transmit light incident upon the transparentsubstrate 118. As shown in FIGS. 4 through 6, the lens 204 is positionedover the color filters 202. It is contemplated that the lens 204 isconfigured to focus and to transmit light incident upon the transparentsubstrate 118 from multiple angles. The lens 204 may be configured as aFresnel lens, a ball lens, a diffractive lens, a diffractive opticselement (DOE) lens, another type of lens, or the like, that isconfigured to collimate the light incident on the lens 204. In animplementation, the lens 204 may be indented. In another implementation,depending upon the configuration of the sensor 200, the lens 204 may beon either side of the transparent substrate 118. Moreover, the lightsensor 200 may include a diffuser 206 next to or in place of the lens204. The lens 204 may take in light from multiple angles and collimatethat light so that the collimated light at least substantially passesthrough the substrate 118 to the color filters 202 and eventually to thephotodetector 108. In one or more implementations, a width (W) of thelens 204 may be approximately 0.52 millimeters (mm). However, the widthof the lens may vary depending on various design configurations of thesensor 200.

It is also contemplated that the light sensor 200 may be configured in avariety of ways. For example, the light sensor 200 may employ no lens204 and instead employ a diffuser 206 and/or an IR suppression filter116. The diffuser 206 and/or the IR suppression filter 116 may beconfigured to also pass through light (in a limited spectrum ofwavelengths to the color filters 202). In another implementation, asshown in FIG. 5, the light sensor 200 may employ both a lens 204 and anIR suppression filter 116 (e.g., an IR interference filter or other typeof filter). As shown, the IR suppression filter 116 is disposed betweenthe transparent substrate 118 and the substrate 102. However, it isunderstood that other IR suppression filter 116 configurations arepossible. The lens 204 is configured to first take in light frommultiple angles and collimate that light so that the collimated light atleast substantially passes through the transparent substrate 118 to theIR suppression filter 116, which passes light in a limited spectrum ofwavelengths (e.g., at least substantially filters IR light and at leastsubstantially passes visible light). The filtered light is then passedto the color filters 202 to further filter the light. The furtherfiltered light from the color filters 202 is then passed to thephotodetector(s) 108 for detection. In the implementation shown in FIG.2, the IR suppression filter 116 may be deposited over the transparentsubstrate 118 and then positioned over the surface 104, or the IRsuppression filter 116. In another implementation, the IR suppressionfilter 116 and/or the diffuser 206 may be integral with the transparentsubstrate 124 (e.g., the IR suppression filter 116 and/or the diffuser206 is manufactured with the transparent substrate 124).

The transparent substrate 118 may be positioned over the substrate 102with the assistance of one or more alignment marks 208. Once thetransparent substrate 118 is properly positioned over the substrate 102,the transparent substrate 118 may be bonded to the substrate 102 with asuitable adhesive material 210. In one or more implementations, thesuitable adhesive material 210 may be a benzocyclobutene (BCB) material,an epoxy material, or the like. The adhesive material 210 is alsoconfigured to at least substantially pass through light incident on thematerial 210.

In an aspect of the present disclosure, the light sensors 200 describedherein may be configured for use as or as part of a gesture sensingdevice. For example an illumination source, such as a light emittingdiode (LED), generates light (e.g., infrared and/or or visible light)that is reflected off an object proximate to the sensor 200. In one ormore implementations, the light sensor 200 may employ only a singleillumination source. However, multiple illumination sources are alsocontemplated. The lens 204 focuses (e.g., collimates) and transmits thereflected light incident on the lens 204 so that the light is passedthrough the color filters 202 and detected by photodetector 108. Asdescribed above, lens 204 may focus and transmit light incident frommultiple angles. The photodetector 108 is configured to generate asignal in response thereto and may provide the signal to one or moreintegrated circuits formed in the substrate 102. The signals may providea basis for gesture based programming including, but not limited to:executing one or more computer programs, executing an application (e.g.,an app), flick scrolling, and so forth.

While FIGS. 4 and 5 illustrate a light sensor 200 that employs aRedistribution Layer (RDL) configuration, it is contemplated that thesensor 200 illustrated and described herein may also employ aBump-On-Pad (BOP) configuration as shown in FIG. 6. The BOPconfiguration may employ a conductive bond pad 126 disposed under thebump interface 136 (e.g., UBM pads).

Example Fabrication Process

The following discussion describes example techniques for fabricating alight sensor that includes at least one color pass filter integratedon-chip (i.e., integrated on the die of the light sensor) and an IRsuppression filter bonded to a transparent substrate. In theimplementation described below, the light sensors are fabricatedutilizing complementary metal-oxide-semiconductor (CMOS) processing andpackaging techniques. However, it is contemplated that light sensors inaccordance with the present disclosure may be fabricated using othersemiconductor chip fabrication/packaging technologies, such aswafer-level packaging (WLP).

FIG. 7 depicts a process 300, in an example implementation, forfabricating a light sensor, such as the example light sensors 100illustrated in FIGS. 1A and 2A. In the process 300 illustrated, one ormore photodetectors are formed in a substrate of a wafer (Block 302). Asshown in FIGS. 8 through 10, the substrate 402 of the wafer may comprisen-type silicon (e.g., silicon doped with a group V element (e.g.,phosphorus, arsenic, antimony, etc.) to furnish n-type charge carrierelements to the silicon) or p-type silicon (e.g., silicon doped with agroup IIIA element (e.g., boron, etc.) to furnish p-type charge carrierelements to the silicon). Thus, the substrate 402 furnishes a basematerial utilized to form the photodetectors 408, the infraredphotodetector 420, the clear photodetector 422, the dark current sensor(not shown in FIGS. 8 through 10), and the bond pad 426. Thephotodetectors 408 may comprise photodiodes, phototransistors, or thelike, formed in the substrate of the wafer using suitable fabricationtechniques such as photolithography, ion implantation, deposition,etching, and so forth.

One or more color pass filters are formed over a surface of thesubstrate (Block 304). The one or more color pass filters are configuredto filter visible light to pass light in a limited spectrum ofwavelengths to the one or more photodetectors. In variousimplementations, the color pass filters may be formed over an adhesionlayer that is configured to adhere the color pass filters to the surfaceon which they are formed (Block 306). In implementation, the color passfilters 410 may be aligned with a respective photodetector 408 to filterlight received by that color pass filter 410 as illustrated in FIG. 9.When formed, the color pass filters 410 may have a thickness ofapproximately one (1) micron. However, it is contemplated that colorpass filters 410 having lesser or greater thicknesses are possible.

A buffer layer is formed over the color pass filters (Block 308). In animplementation, as illustrated in FIG. 10, the buffer layer is formedsuch that the buffer layer at least substantially encloses the colorpass filters (Block 310) using a suitable deposition technique. In animplementation, the buffer layer 414 may be comprised of a polymer layer(e.g., a BCB polymer, or the like) and is configured to at leastsubstantially encapsulate the color pass filters 410.

In an implementation, IR suppression filter is formed on a transparentsubstrate (Block 312) that is configured to facilitate formation of theIR suppression filter as well as furnishing support to the IRsuppression filter. The IR suppression filter may be deposited over thetransparent substrate (Block 314). In an example implementation, the IRsuppression filter may comprise a multi-layer structure that includes atleast two (2) different materials that comprise different refractiveindices. In such implementations, the various materials of the IRsuppression filter 416 may be formed on the transparent substrate 418via various deposition techniques (e.g., sputtering) as shown in FIG.10. However, it is contemplated that other techniques may be employed,including, but not limited to: chemical vapor deposition (CVD),electrochemical deposition (ECD), molecular beam epitaxy (MBE), andatomic layer deposition (ALD). When formed, the IR suppression filter416 may be approximately one (1) to approximately fifteen (15) micronsthick and/or approximately ten (10) to approximately one hundred andtwenty (120) layers thick. However, it is contemplated that the IRsuppression filter 416 may have other constructions and/or thicknesses.In an implementation, the transparent substrate 418 includes one or moreapertures such that when the IR suppression filter 416 is formed on thetransparent substrate 418, and the IR suppression filter 416 includesone or more apertures aligned with the apertures of the transparentsubstrate 418. The sensor 400 may also include dark edges (as describedabove and shown in FIG. 1D). In one or more implementations, the darkedges may be formed over the buffer layer 414, over the IR suppressionfilter 416, or over the transparent substrate 418 to at leastsubstantially eliminate impingement of light that does not pass throughthe IR suppression filter 416.

Once the IR suppression filter is formed on the transparent substrate,the IR suppression filter and the transparent substrate are positionedover the buffer layer (Block 316). Once positioned, the IR suppressionfilter is bonded to the buffer layer (Block 318) which is used to adherethe transparent substrate and the silicon substrate together and to holdthe transparent substrate in the desired position. The transparentsubstrate 418 and the IR suppression filter 416 are positioned over thebuffer layer 414 such that the transparent substrate 418 and the IRsuppression filter 416 at least substantially cover the color passfilters 410 and the photodetectors 408, 422.

FIG. 11 depicts a process 500, in an example implementation, forfabricating a light sensor, such as the example light sensors 100illustrated in FIGS. 1B and 2B. As illustrated, one or morephotodetectors are formed in a substrate of a wafer (Block 502). Then,one or more color pass filters are formed over a surface of thesubstrate (Block 504). As illustrated in FIGS. 1B and 2B, the color passfilters 110 are aligned with a respective photodetector 108. A firstbuffer layer is then formed over the color pass filters (Block 506). AnIR suppression filter is formed over the first buffer layer (Block 508),and then a second buffer layer is formed over the IR suppression filter(Block 510). Next, a third buffer layer is formed over a transparentsubstrate (Block 512). The transparent substrate is positioned over theIR suppression filter so that the transparent substrate can be bonded tothe substrate with the third buffer layer (Block 514). The third bufferlayer may be utilized to adhere the transparent substrate to the siliconsubstrate (e.g., the wafer). For example, the third buffer layer isbonded to the second buffer layer that is formed over the IR suppressionfilter.

FIG. 12 illustrates an example process 600 for fabricating the lightsensors, such as the light sensor 200 shown in FIG. 12. FIGS. 13 through27 illustrate sections of example substrates (e.g., wafer sections) thatmay be utilized to fabricate light sensors 700 (such as sensor 200)shown in FIG. 4. A wafer, such as the silicon wafer 702 shown in FIG.13, includes a first surface 704 and a second surface 706. One or moreintegrated circuits (not shown) and one or more photodetectors 708 areformed in the wafer 702 proximate to the first surface 704. Theintegrated circuits are configured to perform multiple functions basedupon the input (e.g., signals) to the circuits. The photodetector(s) 708is configured to detect light (e.g., visible and infrared) and generatea signal in response thereto. The photodetector 708 may be implementedas a photo sensor diode, a phototransistor, and so forth.

As shown in FIG. 14, an interlayer-dielectric (ILD) layer is formed overthe wafer (Block 602). For example, an interlayer-dielectric layer 709may be deposited over the first surface 704 with one or more suitabledeposition techniques. The interlayer-dielectric material 709 may be alow-k material, and so forth. In one or more implementations, thematerial 709 may be about 1 micron to about 1.3 microns in thickness. Ametal layer is then formed over the interlayer-dielectric layer (Block604). The metal layer 710 illustrated in FIG. 14 may be a metal onelayer (e.g., aluminum), or the like. Forming of the metal layer mayinclude depositing the metal layer 710 over the layer 709 with suitabledeposition techniques and then patterning the metal layer 710 to formone or more conductive layers 712, as well as alignment marks 714. Apassivation layer is then formed (e.g., deposited) over the patternedmetal layers and the ILD layer(s) (Block 606). The passivation layer 716illustrated in FIG. 15 may be an oxide layer, or the like. In one ormore implementations, the passivation layer 716 may insulate the metallayers 710 (e.g., conductive layers 712, alignment marks 714) from laterfabrication steps.

As shown in FIG. 15, an edge trim region 717 is formed about the edge715 of the wafer 702 through suitable etching techniques. The edge trimregion 717 may be comprised of various dimensions depending upon therequirements of the wafer 702 (e.g., attaching the transparentsubstrate). In a specific example, the edge trim region 717 may have adepth (“ED”) of about one hundred and fifty microns (150 μm) and a widthof approximately five millimeters (5 mm). However, the edge trim region717 may have other dimensions depending upon the fabricationrequirements of the wafer 702. For example, the depth of the edge trimregion 717 may be less than one hundred and fifty microns (150 μm) insome implementations or greater than one hundred and fifty microns (150μm) in other implementations. In another example, the width of the edgetrim region 717 may be less than five millimeters (5 mm) in someimplementations or greater than five millimeters (5 mm) in otherimplementations. One or more color filters are then formed over thepassivation layer and over the adhesion layer (Block 608). As describedabove, the color filters 718 allow light in a limited spectrum ofwavelengths to pass through the filter, while blocking (e.g., reflectingor absorbing) light within a second spectrum of wavelengths. In one ormore implementations, the color filters 718 are configured as absorptionfilters. As shown in FIG. 16, the color filters may be a red colorfilter 718A or a green color filter 718B formed over the photodetector708. The color filters 718 are held at least substantially in positionwith a suitable adhesive (e.g., bonding) material 719. While FIG. 16only illustrates red and green color filters, it is contemplated thatother color filters may be employed (e.g., blue, magenta, cyan, etc.)depending on the requirements of the sensors 700. Moreover, while thecolor filters 718A and 718B are shown stacked upon each other, it isunderstood that individual color filters 718 may be deployed over thepassivation layer 716 and over individual photodetectors 708 (e.g., asingle color filter 718 deployed over a single photodetector 708) in anon-stacked configuration.

An adhesive material is then formed over the passivation layer, theadhesion layer, and the color filters (Block 610) for permanent bonding.The adhesive material 720 shown in FIG. 17 may be a benzocyclobutene(BCB) material, an epoxy material, or the like. In one or moreimplementations, the adhesive material 720 is configured to at leastsubstantially pass light through the material 720. A transparentsubstrate is then bonded to the wafer with the adhesive material (Block612). In one or more implementations, the transparent substrate 722 (seeFIG. 18) may be a glass wafer, or the like. The transparent substrate722 may include a protective layer 724 to protect the transparentsubstrate 722 from later fabrication steps. Moreover, the transparentsubstrate 722 may further include a standoff layer (not shown) that isconfigured to protect a lens (described herein) from pressure exerted ona transparent substrate 722 surface proximate to the lens. The substrate722 is also configured to at least substantially pass light incidentupon the substrate 722. As shown in FIG. 12, the silicon wafer issubjected to a backgrinding process and then re-oriented (Block 614).The second surface 706 of the wafer 702 is subjected to a backgrindingprocess (see FIG. 19) with any suitable backgrinding techniques (e.g.,chemical-mechanical planarization, etc.). The alignment marks 714 may beused to properly align the wafer 702 with the transparent substrate 722through one or more suitable alignment techniques. The sensor 700 isre-oriented so that the transparent substrate 722 is oriented to thebottom with respect to the wafer 702 for further fabrication steps. Oncethe silicon wafer is re-oriented, an oxide layer is deposited over thesecond surface (Block 616). In one or more implementations, the oxidelayer 726 may be a silicon dioxide layer, or the like, that forms ahardmask region (see FIG. 20).

A through-substrate via (TSV) is then formed in the wafer (Block 616).As shown in FIG. 20, a photoresist layer 728 is first deposited over theoxide layer 726 to allow for patterning of the TSV 730. A selectedregion of the photoresist layer 728 is patterned to allow for etching ofthe TSV 730. The selected region is then etched through the siliconregion 732 to form the TSV 730. As described above with respect to FIG.4, the TSV 730 allows for electrical interconnects to be formed in thelight sensor 700. The photoresist layer 728 is then removed through oneor more suitable stripping techniques. Once the photoresist layer 728 isremoved, a liner material 734 may be deposited over the light sensor 700and in the TSV 730 (see FIG. 21). In one or more implementations, theliner material 734 may be a suitable liner material, such as a silicondioxide material, a nitride passivation material, or an organic polymer.A spacer etch may be performed to etch any unwanted liner material 734.For example, the spacer etch may remove liner material 734 to at leastpartially expose the conductive layer 712A (e.g., contact pad). As shownin FIG. 12, an isolation material is then deposited in thethrough-substrate via (Block 618).

A conductive material is then deposited in the TSV (Block 620) to forman electrical interconnect. For example, as shown in FIG. 22, a barrierand seed metal 736 is deposited in the TSV 730 and over the sensor 700.The barrier and seed metal 736 may then be patterned throughphotolithography, or the like. A conductive material 738 is then platedover the seed metal 736 to form the electrical interconnections in theTSV 730 (see FIG. 24). In one or more implementations, the conductivematerial 738 may be copper, or the like. Moreover, the conductivematerial 738 may have a thickness of approximately six (6) microns. Asshown in FIGS. 23 and 24, a resist mask 740 is also formed (e.g.,deposited) to prevent formation of the conductive material 738 in themask 740 regions. In one or more implementations, the resist mask 740may be comprised of a negative resist material, or the like.

The under-bump metallization region is then formed over the wafer (Block620). Referring to FIGS. 25 and 26, the mask 740 and the seed metal 736under the mask 740 are stripped away. The seed metal 736 and the maskregion 740 may be stripped away with one or more suitable etchingtechniques. For example, the etching techniques may include a wet etch,or the like. A passivation layer 742 may then be formed over the wafer702 (e.g., over the conductive material 738) to insulate the conductivematerial 738 from the later fabrication steps. The passivation layer 742may be comprised of a BCB material, a polyimide layer, or the like. Asshown in FIG. 27, the UBM region 744 is formed over the conductivematerial 738. For example, the passivation layer 742 is selectivelyetched and then a UBM conductive material 746 is deposited over therecently etched passivation layer 742 area for formation of the UMBregion 744. A solder bump is subjected to a reflow process to the UBMregion 744 to provide an electrical interconnect between the sensor 700and a corresponding PCB pad. It is further contemplated that thetransparent substrate 722 includes a lens as described above and shownin FIGS. 4 through 6. The lens may be a Fresnel lens, a ball lens, adiffractive lens, or another type of lens that may be pre-formed in thetransparent substrate 724 or formed after formation of the UBM region744. Moreover, the transparent substrate 724 may include a diffuser inaddition to or in place of the lens. Suitable wafer-level packagingprocesses may be utilized to segment and package the wafer 702 intoindividual die.

CONCLUSION

Although the subject matter has been described in language specific tostructural features and/or process operations, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A light sensor comprising: a substrate having asurface; a photodetector formed in the substrate proximate to thesurface, the photodetector configured to detect light and to provide asignal in response thereto; at least one color filter disposed over thephotodetector, the at least one color filter configured to pass light ina limited spectrum of wavelengths to the photodetector; and atransparent substrate disposed over the substrate, the transparentsubstrate including a diffuser configured to diffuse light incident onthe diffuser and to pass the diffused light to the at least one colorfilter, wherein the at least one color filter includes a first colorfilter configured to filter visible light and to pass light having afirst limited spectrum of wavelengths and a second color filterpositioned over the first color filter and configured to filter visiblelight and to pass light having a second limited spectrum of wavelengths.2. The light sensor as recited in claim 1, further comprising a firstconductive layer and a second conductive layer and a through-substratevia configured to electrically connect with the photodetector.
 3. Thelight sensor as recited in claim 1, wherein the at least one colorfilter is at least substantially transparent for light within the firstspectrum of wavelengths and at least substantially opaque for lightwithin a second spectrum of wavelengths.
 4. The light sensor as recitedin claim 1, further comprising an IR suppression filter disposed overthe surface, the IR suppression filter configured to filter infraredlight to at least substantially block infrared light from reaching thephotodetector.
 5. The light sensor as recited in claim 4, wherein the IRsuppression filter comprises an IR cut interference filter.